I was messing around with my alt bomber which had a bomb and a blaster. Being effective on all monsters is very helpful, and the minor knockback helps a ton, especially for pushing monsters juust out of range of attacking you (that is, when they are attacking you)

Nova driver is nice for PVE (for elementa-weak families) because of its higher damage. Storm driver is a good second, though depending on what you're fighting, the shock can help slow enemy movement down. This can be a good or bad thing.

For PVP, I think storm driver is the best damaging/utility gun, since shock is an amazing status. Valiance as a good 1v1/kiting gun though.

To be fair, the valiance was great before the buff.

A very small group of us used it in ld before it was common (i was inspired by thisnameisinuse, who was the first effective user), and for pve it was great for all the same reasons it is great now.

On topic:

You can see the patch notes here.
The blaster line was givein a small amount of knockback.
The bullet speed increase was nice but not important.
The patch also increased gun damage overall.

You can try your super blaster out and see if you like the style before upgrading it to a valiance. The only difference will be the knockback on the valiance is a bit larger.
The voltech alchemer will also be similar to a storm driver, except there are more ricochets as you move to 5*. Look in the wiki for more details.

Obviously, I would recommend the valiance too. It's the most satisfying single gun to use (excluding things like dual-drivers switching.)
- The polaris/supernova is annoying with its slow bullet speed. You are right that that knockback is annoying in teams, and if you play in teams frequently, you wouldn't use it very often. When solo, it is effective, but you can't help feel like you are just shooting a wall of spam to get through a level.
- As a sidearm, I would advise against the storm driver. The two shot limit of alchemers is annoying as it means slow breaking of blocks and minerals. The slower bullet speed and narrow hit box means you need to place your shots right, and this is not even considering ricochets. For someone who is bombing, you have enough to think about, so I would think it would just be too frustrating or inefficient. If you were planning to play with only guns, then it's not too bad.
- An AP is useful for its fast block breaking and mineral breaking capabilities and anti-turret damage, but there is no knockback (which is useful or not, depending on the situation) and it's not nearly as satisfying as the valiance. You have a silversix, so I'm sure you already understand. It was buffed in February to be pure elemental, so it's more useful outside of fsc.

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As to a helmet, will you ever do gun-gun? If not, then you should get a helmet that will benefit the sword since it will give you more damage. A shadowsun will give some damage on your gun, but you'd get more damage from a skolver cap on your sword. The only exception would be that your gun is your main source of damage and the sword is only when something happens to come close.

What swords will you be using btw? UV?

Your situation is not a full gunslinger, so don't worry about not having to have posted in that.

I would sell the 3 variant ticket (160k cr?)
You would be better off rolling 8 times than using the ticket once.
Or crafting over time, as you already suggested.

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If you are going to be using a glacius, I would not do the storm driver since you would have nothing to kill gremlins and beasts effectively. That being said, gunning them in with a valiance is a pain, so I would suggest getting that thorn blade to attack them both for when the glacius would be useful for a level. I suppose you could bomb with your nitro.

I'm not a gunner but I'm a bomber that has used guns. I think polaris is a very good weapon for bombers. We really don't have a good answer against turrets other than getting close to them and polaris does a good job at attack cancel/turret sniping. As far as annoying your teammates, yes it can be annoying if you use it wrong. I'm assuming you're good at using nitronome as CC in group situations; the polaris isn't much different and bombers will definitely pick it up and use it more effectively faster than other people who aren't used to using knockback as CC.

I'm not sure what you plan on removing for your gun though. When I ran polaris I did a polaris + 3 bomb loadout but I ended up switching back to glacius because cleanup duty is a lot faster with a sword.